The present invention relates to a touch control apparatus for an electronic keyboard instrument.
It is known that, in an electronic musical instrument, a touch responsive control is carried out to control tonal characteristics according to key depression touch. The touch responsive control is generally classified into an initial-touch control wherein intensity of key depression in the course of depression or just upon the key depression is sensed to control a tone, and the after-touch control wherein intensity of key depression when or after a key has been fully depressed is sensed to control a tone. The initial touch control is usually utilized to make a tone loud when a key is depressed intensively while the after-touch control usually makes for a tremolo effect, vibrato effect and tremolo speed control, etc.
In order to achieve such special sound effects, a conventional touch control apparatus is provided where some control switches, such as a tremolo switch, are provided so as to obtain a desired sound. In another conventional touch control apparatus, depressions of the keys are utilized to obtain the special sound effects. Such touch control apparatus utilizing keys is known as a key depression pressure detection apparatus for an electronic musical instrument as disclosed in Japanese Utility Model Preliminary Publication No. 50-121726. This detection apparatus comprises a horizontal electrode substrate, a horizontal elastic conductor opposing the electrode substrate, a pair of elastic insulators inserted therebetween along long sides of the electrode substrate and the elastic conductor, and a flexible electrode plate conductively fixed on the upper surface of the elastic conductor along its long side. When a key is depressed, the elastic conductor is deflected downward to change a contact area and a contact pressure with the electrode substrate in accordance with a magnitude of the depression force, thereby performing the after-touch control operation.
There is a problem with the manufacture and assembly of such a conventional key depression pressure detection apparatus. Since a pair of elastic insulators is required, the number of components is increased, resulting in cumbersome manufacture and assembly. In addition, if the elastic insulators are not mounted exactly parallel to each other, the degree of deflection differs along the longitudinal direction. As a result, a resistance changes, and the quality of the apparatus is degraded.
In order to solve the above problem, another conventional touch control apparatus (Japanese Utility Model Preliminary Publication No. 59-9399 of the same applicant) is proposed wherein a sensor and a damping member are stacked in a case, and the sensor is made of an elastic resistor and a pair of conductive plates mounted on the upper and lower surfaces of the resistor.
However, according to this touch control apparatus, an extra case must be used to align the stacked members and electrically insulate the stacked members from other members.